Trained negotiators and armed officers were deployed to the scene and road closures put in place on Norfolk Street and around the car park entrance to ensure the safety of the public.
The two boys and the man were brought safely out of the room at just before 7am and the roads were reopened.
No one was injured in the incident. However, all three are believed to be intoxicated and have been taken to Hull Royal Infirmary as a precaution.
Detective Chief Inspector Stewart Miller said: “An investigation has been launched and we’re working to understand the circumstances of the incident. We believe this to have been an isolated incident, with no risk to the wider public.”
If you have any information about the incident and you have not yet spoken to the police, please call 101 quoting log number 95 of March 26.